In the past, the low viscosity liquid wastes from paint, adhesive or ink manufacturing facilities were recycled for use as cleaning solvents in the corresponding factories. The processes used were limited to the simple distillation or the recovery of solvents azeotropically with water. Following the recovery of the solvent, the water was recycled to the boiler by siphon.
None of the prior art processes involved the treatment or recovery of solvents from ink or paint wastes other than the recovery for use as a cleaning agent or some other limited industrial application. It is well known that a cleaning solvent has only limited uses as a diluent. For technical reasons, many formulating parameters should be determined prior to classifying a particular solvent as a diluent in the technical meaning of the word when such solvent has been labeled as a cleaning solvent.
In order to have a good, solvent-based resin matrix, a coating, an adhesive or an ink, it is necessary that the dilution parameters be defined. This could not be possible unless the solvent proportions are very well determined. It is therefore necessary that, when solvents are recovered from the wastes, separation of the solvents be specific.
One of the economic and technical setbacks of the previous processes was the difficulty in separating the hydrophilic solvents (or those that are water soluble) which are very common in the industry from water. Examples of those solvents include ketonic or alcoholic compounds and especially glycols which are highly soluble in water in all proportions and consequently non-recyclable because the water must in all cases be separated from those solvents. The present invention eliminates those technical problems that weighed heavily on previous procedures.
Other problems also arise in prior processes, such as the thermosetting of mud resulting from reactive resins in the presence of water. This causes an industrial-scale operation to be non-viable due to efforts and time required for the removal of the coagulated mud and the cleaning up of the mixer-reactor.
In the apparatus of the present invention, the heating of the liquid waste in the mixer reactor is effected by flowing a thermal fluid through a circular serpent coil which is spread over substantially the entire exterior wall of the reactor and which is circumvented by a an exterior insulator. In that manner, a homogeneous heating all over the heated area with minimum loss of energy is accomplished.
A flexible hose links the outlet of the mixer-reactor to a fractionating column which has many theoretical plates. The fractionating column is connected to a condenser where the first distillate is condensed. The condensed distillate is received in a column which has a level indicator for the volumetric determination of the distillates.
According to the identity of the recovered distillates, the condensed liquid is transferred by a discharge pipe to one of six tanks through two valves, the first valve being at the outlet of the column and the other being at the inlet of the aimed tank. The outlet of each of the six tanks is connected to a seventh tank which is the blending tank to be used for the production of the diluents by mixing distillates from the six tanks.
The process of the present invention is practical, efficient, and simple and differs extensively from other prior processes in that it employs fractional automation, it achieves high yield that could reach up to 95% of petrochemical solvents from the waste liquid volatile, and it produces solvents which are free of color contamination when the waste in question is coming from paint, ink or dye facilities.
Another advantage of the present invention is the absence of danger resulting from pressure build-up caused by mud stacking on the mixer-reactor walls. In the present invention, continuous movement caused by a central rotary anchor of the mixer-reactor vessel ensures homogeneous heating of the mixture. This aspect was absent in the prior procedures which did not take into consideration the piling up of mud in the bottom part of the mixer-reactor even at the time when it reached a level of 20%.
The adopted procedure did not develop the part where the piled up waste in the bottom of the boiler or reactor vessel prevents the spread of heat to the upper levels of the reactor which carries dangers in developing internal pressures mainly when it is the case of a localized heating in the bottom part.
The present invention overcomes the disadvantages of the prior procedures in addition to the fact that it brings a new concept for regenerating solvents used as diluents by the selected fractioning procedure that allows the categoric separation of solvents while minimizing as much as possible the presence of an azeotrope.
These and other objects and advantages of the present invention will be apparent from the following description.